In hermetic electromotive compressors, an internal protective device is typically employed for detecting excess current that flows to the motor and abnormally high ambient temperature when an abnormal situation such as running under an excess load or a coolant gas leak, etc., develops. The internal protective device contains a bimetal switch that senses excess current or abnormal temperature in the atmosphere and, if an abnormal situation is detected, the contact of the bimetal switch is opened and the circuit is shut off, thereby protecting the motor from any possible damage.
In an electromotive compressor, an air-tight terminal or a fusite pin assembly (C: a common terminal, M: a main winding terminal, and S: an auxiliary winding terminal) is provided for the purpose of connecting the windings of the motor and an external power supply source and the internal protective device is connected to the C pin of the fusite pin assembly.
Separate from protection based on the bimetal switch, an Integral Back-up Protection System (IBPS) element which has a fuse function of instantaneously shutting off an abnormal current which is dozens of times greater than the rated current that flows which would cause contact deposition of the bimetal switch or short-circuiting of the motor winding. The IBPS element is connected in series with the bimetal switch and, along with the bimetal switch, it is installed in the electromotive compressor.
As an example of technology of this kind, the structure of the installation of a protector for hermetic type electromotive compressors is disclosed in Toku Kai Hei 10-89254. The protector has a heat-responsive switch, an insulated holder that holds a receptacle and a connective terminal and connects the receptacle to the electrically conductive terminal of a glass air-tight terminal of a hermetic electromotive compressor.
Nevertheless, the internal protective device for the electromotive compressor according to the prior art has had the following problems:
In hermetic electromotive compressors, the position for the installation of the internal protective device at the air-tight terminal (fusite pin), its size and its direction can be different, depending upon the internal specifications of the compressor manufacturers. Because of this, the internal protective devices have to have a design specification that meets the requirements of the manufacturers.
For example, the space for the installation of the internal protective device (the shape of the space) can be different, depending upon the arrangement of the common terminals (C), the main winding (M) and the auxiliary winding (S) of the fusite pin assembly of the electromotive compressor, the direction of the winding and the position of the exhaust pipe, etc. Thus, it has been necessary to design internal protective devices having different configurations in order to fit such spaces.
Varying the metal mold for a modification of the shape of a plastic insulative housing that is a part of the internal protective device or changing the connective tool for the receptacle, etc., leads to an increase in the cost, thereby making it difficult to offer a protective device at low cost.